Nowadays, many power stations and power transmission stations such as converter stations are established in dry and water-shortage regions of North China, where due to high environment temperature and significant water evaporation in summer, water resources are more precious. However, if equipments of power stations and power transmission stations such as converter stations are cooled with traditional water cooling methods, the scarce water resources in those regions may be exhausted. Thus, all of the cooling equipments generally used in these power stations utilize air coolers. Because converter stations are always located in geographical positions having relatively lower environment temperature, the utilization of air coolers may meet the cooling requirement of a converter valve, which is a kind of processing equipment used in power stations, and the satisfied cooling effects may be achieved.
However, some regions have such high temperature that the air coolers cannot cool the fluid to environment temperature, thereby limiting the application of the air coolers in such dry regions. For example, in some places in Northwest China, the highest extreme environment temperature may come up to 44° C., while the highest inlet valve temperature that is permitted by a converter valve as a core equipment of DC transmission projects is only 40° C. In this situation, pure water used for the converter valve cannot be cooled by the air coolers. On the contrary, the air coolers may heat the cooling water. Thus, it is not suitable to only adapt air coolers in this situation.
Also, because power generation and power transmission equipments generally enter maximum operating conditions in the hottest days in summer when environment temperature reaches its highest extreme value, the air coolers may usually not provide enough cooling capability in this case. As a result, the converter stations have to operate with reduced payloads, as well as lowered power levels, which may cause significant economic loss and an adverse effect on the development of national economy.